The present invention relates to an acceleration/deceleration system for a numerical controller.
A jog feed, a quick feed, a manual handle feed, a step feed and like manual operations are known means for an operator to move a machine tool to a desired position, as by a push-button manipulation during automatic running of a numerical controller which controls movements of the machine tool in the X-, Y- and Z-axis directions through commands from a tape. Also when the machine tool is driven in the same axis superimposing two or more kinds of pulse distribution commands (as in the case of effecting such a manual intervention in the automatic running of the numerical controller), it is necessary that the commands be subjected to acceleration or deceleration processing prior to their application to a servo control circuit. To meet this requirement, it is general practice in the prior art to employ an arrangement in which pulses distributed separately by automatic and manual mode distributors 1 and 2 are added together by an adder 3 and the adder output is subjected to exponential type acceleration or deceleration processing by an acceleration/deceleration circuit 4, thereafter being provided to a servo control circuit 5 to drive, for example, an X-axis motor 6, as shown in FIGS. 1 and 2. FIGS. 2A, 2B, the broken line in FIG. 2C and the solid line in FIG. 2C respectively show time vs. pulse frequency characteristics of the outputs from the automatic mode distributor 1, the manual mode distributor 2, the adder 3 and the acceleration/deceleration circuit 4.
In recent years, however, there has come into general use a system which effects the acceleration or deceleration along a commanded path in the hope of moving the tool with a minimal deviation therefrom. With this system, a tangential-direction velocity is subjected to acceleration or deceleration processing by an acceleration/deceleration circuit 7 prior to a linear or circular-arc interpolation by the automatic mode distributor 1, as depicted in FIGS. 3 and 4. Consequently, in the case of a manual intervention, the distribution pulses from the manual mode and automatic mode distributors 2 and 1 are added together by the adder 3, as shown in FIG. 3, and the superimposed distribution pulses can no more be subjected to the acceleration or deceleration processing. The reason for this is that if the output pulses from the automatic mode distributor, which have already been subjected to acceleration or deceleration processing, were further subjected to acceleration or deceleration processing, then the path of the tool would deviate from a commanded one. Therefore, assuming that the time vs. pulse frequency characteristics of the outputs from the acceleration/deceleration circuit 7, the automatic mode distributor 1 and the manual mode distributor 2 are such as shown in FIGS. 4A to 4C, respectively, the characteristic of the input pulse to the servo control circuit 5 will be as depicted in FIG. 4D, making it impossible to achieve a smooth acceleration or deceleration.